Trafficking people for forced labour and sexual slavery has become the world's number two most lucrative crime, and terrorists are using shadowy underground networks to move around, a senior US counter-trafficking official warned yesterday. Human trafficking, particularly the smuggling and enslavement of young women for prostitution, is tied with weapons smuggling as the second-largest illegal moneymaking activity, said T March Bell, the US Justice Department's senior special counsel for trafficking issues and civil rights.

Only the narcotics trade reaps more profits for organised crime, but traffickers are earning billions of dollars exploiting tens of millions of victims each year, Bell said, calling it "the No 1 human rights issue today".

The profits are huge, he told reporters, citing the example of a brothel owner in Southeast Asia who typically might pay $8 000 for a young woman. "We think that owner can make a $200 000 profit on that $8 000 investment," Bell said. Although the traffickers are dealing mainly with young women peddled to brothels or men, women and children sold into virtual slavery on farms and in factories, "they're moving any kind of people for a price", Bell said.

Despite the massive scale of the crime, law enforcement agencies are having a difficult time bringing perpetrators to justice - in part because of corruption within their own ranks.

In the former Yugoslavia, there have been numerous cases of corrupt local police officers engaged directly in the sex trade or willing to alert a bordello operator to an impending police raid in exchange for a bribe.

Police officers in many poor, developing countries where trafficking is widespread tend to be poorly paid, making them particularly susceptible to bribes, Bell said. In Cambodia, the average officer earns just $35 a month, he said.

Local and national police agencies are trying to counter that by improving the training of police officers, ensuring they are paid professional salaries, and making anti-trafficking units the envy of police forces by equipping them with the latest technology and holding them to higher standards, Bell said.

While the most effective weapon against traffickers is "street-level law enforcement", police agencies increasingly are turning to undercover operations in an effort to infiltrate clandestine rings, he said.

In the United States and many European countries, former victims are getting increased protection and refugee status in the hopes of persuading them to testify against their former captors, Bell said.

A key challenge is winning the trust of former victims who all too often are "frightened, scared, intimidated and coerced" by traffickers. "Unless a victim feels safe, they're not going to provide much information to prosecute the perpetrators," he said.